Electrical insulating structure



Jan. 31, 1967 FQRSHA 3,302,149

ELECTRICAL INSULATING STRUCTURE Filed Sept. 50, 1964 2 Sheets-Sheet 1 .FIGZ.

United States Patent 3,302,149 ELECTRICAL INSULATING srauc'ruau Herbert E. Forsha, Sharon, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corpora- This invention relates in general to electrical inductive apparatus, and more particularly to electrical insulation structures for electrical inductive apparatus.

The electrical insulation, structures for electrical inductive apparatus, such as transformers of the core form type, are presently constructed of sheets of insulating material having predetermined widths and lengths, with strips of insulating material glued thereto in spaced parallel relation across the Width of the strips at predetermined intervals. If the insulating structure is to be disposed between high and low voltage winding sections, the sheet of insulating material with the glued strips attached thereto is formed into a circular shape. Other sheets of insulating material of predetermined differing lengths, also having strips of insulating material glued thereto, are also formed into circular shapes.

All of the circular shaped insulating sheets are then concentrically disposed to form an insulating barrier having the desired wall thickness. The glued strips of insulating material are perpendicular to the circumference of the circular insulating sheets and provide ducts through the structure for fluid dielectric fluid to penetrate.

If the insulation is required between the electrical windings and the casing of the transformer, or between the different phases of a polyphase transformer, the sheets of insulating material with the insulating strips glued thereto, are stacked together to form a barrier having a predetermined thickness.

The gluing of individual strips of insulating material to the insulating sheet material is slow and costly. The bending of the sheets to form circular members, and the disposing of the circular members in concentric relation to obtain the desired barrier thickness is also a slow and costly process. Further, the insulating barriers must be custom made for each transformer rating. Also, a plurality of different lengths of insulating strips must be stocked, as well as a plurality of strip lengths, to form the different diameters of strip material that will nest in close, concentric relation to form one integral structure.

It would be desirable to eliminate the gluing of individual insulation strips to the sheets of insulating material, and it would also be desirable to eliminate the formation of individual circular members which are concentrically disposed to obtain the desired buildup.

Accordingly, it is an object of this invention to provide new and improved electrical insulating structures for electrical inductive apparatus.

A further object of the invention is to provide new and improved electrical insulation structures for electrical inductive apparatus of the core form type, which provides the barrier thickness desired and ducts for fluid coolant.

Another object of the invention is to provide a new and improved electrical insulating structure in which the insulating sheet is uncut until the final barrier thickness is obtained.

A further object of the invention is to provide a new and improved electrical insulating structure in which the insulating sheet material is uncut and the duct forming members are continuously disposed about the circumference of the insulating structure and interleaved with the insulating sheet material.

Briefly, the present invention accomplishes the above cited objects by forming the insulating structure out of a continuous strip of sheet electrical insulating material. A plurality of turns of the sheet insulating material are first wound to form an insulating tube having the desired thickness and strength, and then a plurality of continuous strips of corrugated insulating material are interleaved with the sheet insulating material to form the ducts. The interleaving ducts may be continuously disposed between the insulating sheet, with the number of turns of sheet insulating material and corrugated strip insulating material being dictated by the thickness of the insulating barrier required by the particular application. Or, the corrugated strips of insulating material may be cut after after one complete circumferential turn and the insulating sheet material may be wound to form more than one turn between ducts. After the desired number of turns of the insulating sheet material are wound between ducts, the corrugated strip insulating material may be introduced again to form another circumferential turn. This procedure and structure is repeated until the desired barrier thickness is achieved. The sheet material is, therefore, continuous throughout the complete insulating structure, eliminating the cutting of the sheet material to different lengths and the forming of individual lengths of sheet material into circular members. The insulating strips are corrugated to form ducts, and are introduced at predetermined intervals across the width of the insulating structure and proceed around the circumference of the structure instead of across its width. The ducts formed by the corrugated insulating strips allow penetration of cooling fluid in a direction parallel with the axis of the insulating structure. Thus, different lengths of insulating strip material are not required to be stocked and manually glued across the Width of the sheet insulating material.

If fiat insulating barrier structures are required, they may be constructed in the same manner, with a continuous sheet of insulating material and continuous circumferentially disposed corrugated strip members, and the round structure flattened to form the desired insulat ing barrier.

Further objects and advantages of the invention will become apparent as the following description proceeds and features of novelty which characterize the invention will be pointed out in particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the invention, reference may be had to the accompanying drawings, in which:

FIGURE 1 is a perspective view of a transformer with the casing of the transformer partially cut away, to show the location of electrical insulating structures which may be constructed according to the teachings of the invention;

FIG. 2 is a perspective view of an insulating structure formed according to the teachings of this invention;

FIG. 3 is a plan view of a winding structure showing a high-low insulation barrier constructed according to one embodiment of the invention; and

FIG. 4 is a plan view of a winding structure showing a high-low insulation barrier constructed according to another embodiment of the invention.

Referring now to the drawings, and FIG. 1 in particular, there is shown a transformer 10 of the core form type, which utilizes electrical insulating structures constructed according to the teachings of this invention. Transformer 10 includes winding assemblies 14, 16 and 18 disposed in inductive relation with a magnetic core 20. Magnetic core 20 may be constructed of a plurality of superimposed, stacked magnetic steel laminations to form upper and lower yoke members 22, and leg members 24, 26 and 27 for receiving winding assemblies 14, 16 and 18, respectively.

Winding assemblies 14, 16 and 18 are similar, each serving a ditferent phase of a polyphase electrical system, and each comprise a low voltage winding 28, a high voltage winding 30, and a barrier interwinding insulation structure 32, disposed between the low and high voltage windings 28 and 30, respectively.

Additional insulating structures may be disposed between the winding assemblies themselves, such as barrier structures 34 and 36, thus forming electrical insulation between the electrical phases, and similar insulating structures may be disposed between the winding assemblies and grounded portions of the transformer 10, such as the barrier structure 38 disposed between casing 12 and winding assembly 14.

The barrier electrical insulating structure 32, which forms the high-low insulation between the low and high voltage windings, 28 and 30 respectively, is shown in greater detail in FIG. 2. Interwinding insulation structure 32 is tubular in shape, having an inside diameter which allows a winding to be disposed therein, and an outside diameter determined by the wall thickness desired. Although FIG. 1, illustrates the winding assemblies 14, 16 and 18 as having one low voltage winding 28 and one high voltage winding 30, requiring one interwinding insulation structure 32, in practice the high and low voltage windings may be split into sections, thus requiring more than one interwinding insulation structure 32.

As hereinbefore explained, these interwinding insulation structures are commonly formed of a plurality of sheets of insulation material having a predetermined width and length, with strips of electrical insulating material being glued across the width of the sheet at predetermined, spaced intervals. The sheets of electrical insulating material are then rolled into a circular shape, and the required plurality are concentrically disposed to form the wall thickness desired. This construction of the prior art is costly and requires sheets of different lengths and widths to be cut and stocked, as Well as requiring different lengths of insulating pieces to be cut and stocked.

FIG. 2 illustrates an interwinding insulation structure which eliminates these disadvantages. The interwinding insulation structure 32 is formed of sheet of insulating material 40 and a plurality of corrugated electrical insulation strips 42. Sheet electrical insulation 40' may be formed of fibrous electrical insulation, such as pressboard, or any other sheet electrical insulation. Sheet electrical insulation 40 remains uncut throughout the structure, allowing it to be removed from a roll of electrical insulating material at the time of assembly. Sheet electrical insulation 40 may be of any predetermined thickness, such as .020 inch, with the width of the sheet 40 being determined by the height of the winding assembly. It will be obvious that the invention is applicable to any flexible thickness of sheet insulation.

The corrugated strips of electrical insulation 42 may also be formed of fibrous electrical insulating material, such as pressboard. The corrugated strip insulation 42 has a succession of parallel ridges and furrows which are permanently disposed perpendicular to the length of the strip. The insulating strip 42 is of suflicient thickness to maintain its corrugated shape when assembled into the interwinding insulation structure 32, with thicknesses of to 7 of an inch being suitable. The width of the corrugated strip 42 and the number of strips disposed in parallel relation with one another and with the edges of the sheet insulation 40 are chosen to provide a solid insulation structure 32. It will be understood that the corrugated strip 42 could be as wide as the sheet insulation 46 itself, thus requiring only one corrugated strip foreach circumferential duct. However, in the interest of reducing the weight and cost of the insulation structure 32, a plurality of narrow strips 42 may be utilized with excellent results. A plurality of electrical insulating strips 42 having a width of one to two inches and disposed four to 4 five inches apart, will produce excellent results, although it will be obvious that other widths and spacings may beutilized.

It will be noted that instead of being disposed across the width of the insulating sheet material 40, corrugated strips of insulating sheet material 42 are disposed parallel with the edges of the insulating sheet material 40, and thus proceed around the circumference of the insulation structure 32. The circumferential ducts formed allow penetration of fluid dielectric through the openings pro= vided by the corrugated strips 42, with the penetration being parallel with the axis of the insulation structure 32.-

One embodiment of the invention is illustrated in FIG. 3, which is a plan view of winding assembly 14, showing interwinding insulation structure 32, along with high and low voltage windings 30 and 28, respectively, and leg 24 of magnetic core 20. The sheet insulation 40 starts at the internal diameter of the interwinding insulation structure 32, as shown at 44, with the sheet insulation 40 being formed into a plurality of turns 46 before the corrugated strip material 42 is introduced, in order to build up an insulating tube having the desired strength. A cold setting adhesive or glue may be disposed between the turns 46 at the start 44 in order to prevent the turns 46 from unwinding after removal from its forming mandrel. After the inner tubular portion has been formed, a plurality of corrugated strips 42 are introduced in spaced parallel relation with one another and with the edges of the insulating sheet material 40, and are continuously interleaved with the insulating sheet material 40 until the desired build or wall thickness is obtained. The outer portion of inter winding insulation structure 32 may also have a plurality of superimposed turns of insulating sheet material 40, to provide an outer tube of predetermined strength.

The interwinding insulation structure 32 may, thus, be simply and inexpensively formed, unrolling sheet insulation material 40 from a roll and starting it on a mandrel having the desired diameter. An adhesive may be placed at the start of the sheet insulation material 40, and the mandrel turned until the desired number of turns 46 have been created. The plurality of corrugated strips 42 are then introduced and the mandrel turned, interleaving the corrugated strips continuously with the sheet insulation 40 until a predetermined buildup is reached. When the desired buildup or wall thickness of the interwinding insulation structure 32 is reached, the corrugated strips are cut and the mandrel turned until the desired number of outer turns of insulating sheet material 40 have been applied. A cold setting adhesive may be applied to the outer turn, and the interwinding insulation structure 32 is complete. If desired, a cold setting adhesive or glue may be continuously applied to the raised surfaces on one or both sides of the corrugated strip material 42, as it is interleaved with the insulating sheet material 40, in order to insure that the corrugated strip material 42 will maintain its initial position within the interwinding insulation structure 32. As shown in FIG. 3, the corrugated strip material 42 forms a continuous spiraled duct 49 which has a plurality of openings 50 throughout the interwinding insulation structure 32, which allows ample space for a fluid dielectric, such as sulfur hexafluoride (SP askarel, or oil, to penetrate.

The embodiment of the invention shown in FIG. 3 thus forms a solid, coherent interwinding insulation structure 32, in which the insulating sheet material 40 may be one continuous length, eliminating the cutting, stocking, and forming of a plurality of different lengths, which in the prior art are then concentrically disposed about a common axis to provide the desired wall thickness. This embodiment also utilizes a plurality of corrugated strips 42, which may also proceed throughout the interwinding assembly 32 uncut, eliminating the necessity of cutting them to length and gluing them individually in spaced, parallel relation across the width of the insulating sheet 40. The insulating sheet 40 and cor- 'and cut.

3 rugated strips 42 may be stocked in roll form until required and the interwinding insulation structure 32 quickly and inexpensively built to the desired wall thickness.

When flat barrier insulation assemblies or structures are required, such as barrier structures 34, 36 and 38 shown in FIG. 1, it is merely necessary to build a structure as taught for the interwinding structure 32, having a wall thickness equal to one-half of that desired for the barrier, and then flatten the circular structure. This will form a flat insulating structure, such as structures 34, 36 and 38, having the desired wall thickness and having cooling ducts provided by the corrugated strips 42.

In the event that it is desirable to have more than one turn of insulating sheet material 40 after each circumferential duct has been formed by the corrugated strip material 42, the interwinding insulation structure 32 may be formed as shown in FIG. 4. In this instance, the corrugated strips 42 are terminated after making one complete circumferential turn, with the insulating sheet material 40 continuing unbroken to form the desired number of turns, between the ducts 51, and the corrugated strip material 42 is then again introduced for another complete turn. This procedure and structure proceed until the desired buildup or wall thickness is obtained.

More specifically, the insulating sheet material 40 starts at 44 and makes a plurality of turns 46 to provide an initial tube having the desired strength. A plurality of corrugated insulating strips 42 are then introduced in spaced parallel relation with one another and with the edge of the sheet material 40, such as at point 52, and they continue the interwinding insulation structure for one turn, at which point they are terminated, such as at 54. The insulating sheet material 40 continues unbroken and forms a predetermined plurality .of turns 56, and then the plurality of corrugated strips 42 are again introduced and interleaved with the sheet insulating material 40 for another substantially full turn, and again terminated. This structure is repeated until the desired wall thickness is obtained, producing a plurality of concentric ducts 51 each having a plurality of openings 50 through the interwinding structure 32, instead of one continuous spiralled duct 49, as shown in FIG. 3.

In the assembly of the embodiment shown in FIG. 4, the insulating sheet material 40 is removed from a roll and started on a mandrel of predetermined size at 44. The mandrel is turned until a predetermined number of turns 46 are formed, and a plurality of corrugated insulating strips 42 are introduced at 52 from a roll, and the strips 42 and the sheet insulation 40 are interleaved for substantially one full turn. The corrugated strips 42 are all cut at the end of the turn, and the mandrel is turned to form the desired plurality of turns 56 of sheet insulating material 40. The plurality of corrugated strips 42 are then reintroduced and are interleaved with the sheet insulation 40 for another turn, at which point they are again terminated. This procedure continues until the desired buildup is achieved.

The tubular interwinding insulating structure 32, constructed as taught in FIG. 4, may also be flattened if desired to form flat barrier insulating structures, such as structures 34, 36 and 38. The embodiment of the invention shown in FIG. 4 also eliminates the cutting, stacking, and forming of sheets of insulating material, as does the embodiment shown in FIG. 3. Although the embodiment shown in FIG. 4 requires the corrugated strip material 42 to be out after each circumferential duct 51 is formed, unlike the embodiment shown in FIG. 3, the corrugated strip 42 does not have to be pre-measured It may be simply withdrawn from a roll as required, and cut-to-suit as the assembly is being wound. Thus, precutting, stocking, and individual gluing of a large plurality of spacer members is not required. A cold-setting adhesive may also be applied at preselected points in the interwinding insulating assembly 32 shown in FIG. 4, as hereinbefore described relative to FIG. 3.

Thus, there has been disclosed a new and improved insulating structure which may be disposed between winding sections in core form transformers, between adjacent electrical phases, and between electrical windings and ground, that is simple and inexpensive to construct. Sheet insulation and spacers do not have to be measured, cut and stocked. Spacers for forming the ducts do not have to be individually glued to the insulating sheet material, and the plurality of sheets of insulating material do not have to be individually bent into tubular form and coaxially disposed. The sheet insulating material 40 and spacer material 42, the latter in the form of corrugated strip, may be stored in rolls until required, and simply interleaved upon a mandrel of predetermined diameter until the required buildup or wall thickness is achieved. The insulating sheet material 40 remains uncut throughout the insulation structure 32. In one embodiment of the invention, the corrugated strip insulating material '42 also remains uncut. In another embodiment of the invention, the corrugated strip material 42 is cut after making one turn, but since the cutting occurs during the interleaving operation, premeasuring, cutting and storing of individual strips of insulating material is eliminated.

While a polyphase transformer 10 has been shown for purposes of illustration, it will be obvious that the teachings of this invention apply to single phase transformers, and to any electrical apparatus where tubular and flat insulating structures are required.

Since numerous changes may be made in the above described apparatus and ditferent embodiments of the invention may be made without departing from the spirit thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. Electrical inductive apparatus comprising:

a casing,

electrical winding means,

magnetic core means,

said electrical winding means being disposed in inductive relation with said magnetic core means to form a core-winding assembly, said core-winding assembly being disposed within said casing,

fluid dielectric means disposed within said casing,

at least one electrical insulating barrier structure having a plurality of ducts disposed therein, said at least one electrical insulating structure providing electrical insulation between predetermined components of the electrical inductive apparatus, said at least one electrical insulating barrier structure including a plurality of continuous turns formed of a strip of electrical insulating sheet material having predetermined length and width dimensions, and a plurality of strips of corrugated electrical insulating material disposed between predetermined turns of said strip of electrical insulating sheet material, said strips of corrugated electrical insulating material having predetermined length and width dimensions, with its corrugations extending across its width dimension, the length dimension of said strip of electrical insulating sheet material exceeding the length dimension of said plurality of strips of corrugated electrical insulating material, said strips of corrugated electrical insulating material being disposed in spaced parallel relation with one another across the width of said electrical insulating sheet material and oriented relative to said strip of electrical insulating sheet material to provide ducts in said at least one electrical insulating barrier structure for circulation of said fluid dielectric means.

2. The electrical inductive apparatus of claim 1 Wherein said strips of corrugated electrical insulating material form a continuous duct between a predetermined plurality of successive turns of said strip of electrical insulating sheet material.

3. The electrical inductive apparatus of claim 1 Wherein said plurality of strips of corrugated electrical insulating material are disposed Within each of certain turns of said electrical insulating sheet material to provide a plurality of substantially concentric ducts in said at least one electrical insulating barrier structure.

References Cited by the Examiner UNITED STATES PATENTS 639,523 12/1899 C-hapin 138l41 5 2,602,035 7/1952 Camilli 336 -60 FOREIGN PATENTS 98,626 11/1924 Austria.

LEWIS H. MYERS, Primary Examiner. E. GOLDBERG, Assistant Examiner. 

1. ELECTRICAL INDUCTIVE APPARATUS COMPRISING: A CASING, ELECTRICAL WINDING MEANS, MAGNETIC CORE MEANS, SAID ELECTRICAL WINDING MEANS BEING DISPOSED IN INDUCTIVE RELATION WITH SAID MAGNETIC CORE MEANS TO FORM A CORE-WINDING ASSEMBLY, SAID CORE-WINDING ASSEMBLY BEING DISPOSED WITHIN SAID CASING, FLUID DIELECTRIC MEANS DISPOSED WITHIN SAID CASING, AT LEAST ONE ELECTRICAL INSULATING BARRIER STRUCTURE HAVING A PLURALITY OF DUCTS DISPOSED THEREIN, SAID AT LEAST ONE ELECTRICAL INSULATING STRUCTURE PROVIDING ELECTRICAL INSULATION BETWEEN PREDETERMINED COMPONENTS OF THE ELECTRICAL INDUCTIVE APPARATUS, SAID AT LEAST ONE ELECTRICAL INSULATING BARRIER STRUCTURE INCLUDING A PLURALITY OF CONTINUOUS TURNS FORMED OF A STRIP OF ELECTRICAL INSULATING SHEET MATERIAL HAVING PREDETERMINED LENGTH AND WIDTH DIMENSIONS, AND A PLURALITY OF STRIPS OF CORRUGATED ELECTRICAL INSULATING MATERIAL DISPOSED BETWEEN PREDETERMINED TURNS OF SAID STRIP OF ELECTRICAL INSULATING SHEET MATERIAL, SAID STRIPS OF CORRUGATED ELECTRICAL INSULATING MATERIAL HAVING PREDETERMINED LENGTH AND WIDTH DIMENSIONS, WITH ITS CORRUGATIONS EXTENDING ACROSS ITS WIDTH DIMENSION, THE LENGTH DIMENSION OF SAID STRIP OF ELECTRICAL INSULATING SHEET MATERIAL EXCEEDING THE LENGTH DIMENSION OF SAID PLURALITY OF STRIPS OF CORRUGATED ELECTRICAL INSULATING MATERIAL, SAID STRIPS OF CORRUGATED ELECTRICAL INSULATING MATERIAL BEING DISPOSED IN SPACED PARALLEL RELATION WITH ONE ANOTHER ACROSS THE WIDTH OF SAID ELECTRICAL INSULATING SHEET MATERIAL AND ORIENTED RELATIVE TO SAID STRIP OF ELECTRICAL INSULATING SHEET MATERIAL TO PROVIDE DUCTS IN SAID AT LEAST ONE ELECTRICAL INSULATING BARRIER STRUCTURE FOR CIRCULATION OF SAID FLUID DIELECTRIC MEANS. 